Rheumatology Advance Access originally published online on August 9, 2006
Rheumatology 2006 45(10):1185-1186; doi:10.1093/rheumatology/kel247
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EDITORIALS |
‘Quality of pain’ in systemic sclerosis
Rheumatology Department, ‘12 de Octubre’ University Hospital, Madrid, Spain
Correspondence to: Patricia E. Carreira, Servicio de Reumatología, Hospital 12 de Octubre, Avda. de Córdoba s/n, 28041 Madrid, Spain. E-mail: carreira{at}h12o.es
In the last three decades, measurement of quality of life has become a standard tool to evaluate the impact of disease and therapies in the field of rheumatology. For many years, patient's questionnaires were considered weak ‘subjective’ measures compared with stronger ‘objective’ measures assessed by health professionals. Nevertheless, this point of view changed for many rheumatologists after the demonstration that patient's questionnaire scores are able to predict mortality in patients with rheumatoid arthritis (RA) more effectively than any traditional measure [1]. Patient-reported outcomes give fundamental information about patient's health, functional status, disease symptoms, treatment preferences, satisfaction and quality of life from their own perspective. The two more extended tools to evaluate quality of life in rheumatic patients are the Health Assessment Questionnaire (HAQ) and the Medical Outcome Study (MOS) Short-Form 36 (SF-36). The HAQ was developed for patients with rheumatic diseases, namely RA, in 1980 [2]. Since it has demonstrated to be reliable, adaptable and easy to use, it has been used in diverse areas, especially in chronic rheumatic conditions. The SF-36, on the other hand, was developed initially to be used in health policy surveys [3]. It has documented validity in normal health population and has also been widely used as a measure of general health status in many rheumatic diseases. These two instruments have been employed in many RA studies, undergone hundreds of validations, translated into more than 60 languages and have become important standards for the Food and Drug Administration and other agencies, the American College of Rheumatology (ACR) and OMERACT among others, for chronic rheumatic diseases [2]. After the RA experience, enormous efforts are being done in the field of evaluating quality of life and functional status in other rheumatic diseases, such as ostheoarthritis, vasculitis, systemic lupus erythematosus or systemic sclerosis (SSc). However, whereas questionnaires for RA functional status are being modified and simplified in order to facilitate their use not only in research studies, but also in the standard care of patients [4], the measure of functional status and quality of life in other diseases, such as SSc, is still in its early beginning.
SSc is a highly complex and heterogeneous disease, with aetiological factors and physiopathological mechanisms essentially unknown. It may affect a wide variety of organs, and SSc patients may present with a different combination of general and organ-specific symptoms, as well as with a very different degree of functional limitations. This heterogeneity, together with the rarity of the disease, makes it difficult to accurately measure the functional impact of the disease in large groups of patients. So the degree of functional impairment caused by SSc has not been so far well characterized. The HAQ disability index (HAQ-DI) has been previously used to evaluate disability in SSc patients in several trials and observational studies. HAQ-DI score highly correlates with total skin score and is a good predictor for survival [5]. The modified Scleroderma Health Assessment Questionnaire (SS-HAQ) has been developed as a more specific version of the HAQ for SSc patients, by adding five specific patient-generated visual analogue scales (VAS) and has been validated in English [5] and French [6].
Pain is the most prominent symptom in the majority of rheumatic diseases, a common reason for primary care consultation and a major source of health care costs. Pain is regarded also as ‘subjective’ information obtained from the patient, and viewed by the clinician as preliminary, and not so important, compared with the critical definitive ‘objective’ data obtained from the physical exam, laboratory tests or imaging procedures. But, in fact, pain is considered a parameter of activity in chronic inflammatory conditions, as RA, and the absence of joint pain is included in the ACR RA remission criteria. Original HAQ-DI contains a pain VAS, mainly used by rheumatologists to measure articular pain in RA [2]. Good correlation for pain VAS in RA has been found with joint swelling and tenderness, but the strongest correlations are seen with the scores for functional and psychological status. In the study by Georges et al. [7] in this issue of Rheumatology, pain from any origin (measured by the HAQ-DI pain VAS) is associated with a decrease in the quality of life perceived by the patients. There is scarce literature about the importance and the impact of pain in SSc, although it is referred to as a symptom of their disease by most SSc patients [8, 9]. In a recent study, pain is the single strongest predictor of physical function in SSc [9]. Nevertheless, studies addressing the source of pain in SSc are lacking. The study by Georges et al. [7] does not address what type of pain is related with the detrimental effect on patient's quality of life. While in RA, pain is defined as articular, pain in SSc may come from many sources: ischaemic lesions of the fingertips or dermal stress lesions, arthralgia or arthritis, joint stiffness and contractures, skin distension or oedema, inflammatory myopathy, oesophageal dismotility with gastro-oesophagic reflux or oesophagitis, intestinal pseudo-obstruction, among others. Many SSc patients refer to having inflammatory articular pain and even true arthritis, although erosive disease is uncommon. In the study by Georges et al. [7], musculoskeletal symptoms, defined according to Medsger [10] severity SSc criteria such as myalgia, muscular weakness or peripheral arthralgia or arthritis, were present in 59% of the patients. The presence of any of these musculoskeletal symptoms decreases both the physical (from 41 ± 11 to 32 ± 11) and the mental (from 44 ± 12 to 39 ± 10) component scores of the SF-36. The study does not report the correlation between musculoskeletal symptoms and disability. In the original description and the validation of the SS-HAQ, the presence of joint pain (referred to by the patients) correlated with the HAQ-DI, and in addition, the HAQ Pain VAS not only correlated with joint pain, but also with other scleroderma-related problems that may cause pain, including digital ulcers, heartburn and tendon friction rubs [5]. From my own experience with SSc patients, although many of them report articular symptoms, pain from ischaemic ulcers in the fingertips is probably their most important source of severe pain. Actually, in the study by Georges et al. [7], the presence of digital ulcers (53%) also decrease both physical (from 42 ± 11 to 31 ± 9) and mental (from 44 ± 11 to 38 ± 10) scores of SF-36. Moreover digital VAS from SSc-HAQ is highly correlated with the physical (R = 0.55) and moderately with the mental (R = 0.32) component scores of SF-36. The same happens in the study with other possible sources of pain, such as Raynaud's phenomenon, gastrointestinal involvement or finger contracture.
Since RA and SSc are clearly two very different entities having, probably, different sources of pain, and since HAQ-DI pain VAS has been mainly used to evaluate patients with RA, several questions arise: can we use the HAQ-DI pain VAS in SSc patients as we use it in RA patients? What kind of pain are we measuring in SSc? Can we compare articular pain with, for instance, pain from ischaemic ulcers or intestinal pseudo-obstruction? The use of HAQ-DI in SSc has received the criticism of ‘the lack of a clear conceptual framework’ [11]. Different investigators have used different modifications of the original HAQ-DI (with or without the VAS pain or the VAS patient global; scoring with different disability indices, including or not the use of aids and devices ...). All these modifications applied in different studies make it difficult to obtain reliable results adequate for the whole community of SSc patients. It has been suggested that HAQ-DI may provide meaningful results in SSc clinical trials only if the concept being measured is clearly defined, the instrument being used is clearly identified and the scoring method clearly described [11]. The same should be applied to pain measurement in SSc patients. The HAQ-DI pain VAS was initially developed to measure articular pain in RA and it will be important to assess its validity for other sources of pain that may be present in SSc patients.
There is another interesting question raised by the study: is pain a sign of disease activity in SSc patients? The differentiation between activity (the potentially reversible part of a disease process) and damage (the irreversible part of a disease process) as well as the assessment of severity (the global impact of a disease process, at any given time, on the patient as a whole or on a specific organ) are essential goals for rheumatologists. Definition of disease activity is particularly difficult in SSc for several reasons: (i) it is a rare heterogeneous disease with a high variability in clinical manifestations (ii) unlike other chronic rheumatic diseases, its clinical course is not characterized by periods of ‘activity’ and remission and (iii) although many efforts have been made, trying to find potential circulating markers, there is a lack of available objective measurements. Also, it shares with other chronic rheumatic diseases the common problems that both active and irreversible lesions can be present in the same patient at the same time and not irrelevant number of patients exhibit an indolent course of the disease. Specific indices reflecting primarily either activity or damage have been developed for other rheumatic diseases with the most important efforts done in the field of RA. After more than two decades of dealing with the problem and after numerous trials and observational studies including large numbers of patients, there is still no consensus about RA measures on disease activity [12], which points out the magnitude of the problem. Articular pain is considered a sign of activity in all the activity indices used in RA, although we all know that pain can also be secondary to the irreversible damage produced by the inflammatory process. Can pain also be considered a sign of activity in SSc? And pain of what source? Recently, a composite disease activity index has been constructed and partially validated by the European Scleroderma Study Group [13]. It includes 10 items; each one has its own weight in the score. Interestingly, several of the items included in this SSc activity index (skin tenderness, Raynaud, ischaemic ulcers, arthritis, etc.) may very well represent sources of pain in SSc patients. It seems from the study of Georges et al. [7] and from the others that pain is one of the most important problems for SSc patients, extraordinarily affecting their quality of life. And doctors caring for these patients should make an exceptional effort to control their pain. We can control pain just as a mere symptom, independent of how active the disease is. But, if pain is a symptom surrogated from active SSc, would it not seem much more and appropriate to try to control the activity of the disease?
The active SSc research community is increasing and various treatment strategies are starting to show some degree of efficacy in this disease. Promising new therapies are emerging as candidates for clinical trials in SSc, therefore, it will be necessary to document quantitatively the degree of improvement achieved by patients. From now, rheumatologists involved in SSc research should try to converge and use the same scales and tools, meaning the same and measuring the same in SSc patients. For many years in RA, it has been considered an intellectual responsibility of the rheumatology community to implement clinical rheumatology as a quantitative science, which has been better accomplished using patient's questionnaires. This practice in SSc will help rheumatology to advance and improve the lives of many patients suffering from this complex disease. We are still far away from RA, but we now have the opportunity to extract the experience from this disease and export it to the study of SSc.
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